1. Field of the Invention
The present invention relates generally to the design and use of medical devices, and more particularly to the design and use of a needle assembly for percutaneously accessing an implantable port connected to a patient's vascular system or other body lumen.
Access to a patient's vascular system can be established by a variety of temporary and permanently implanted devices. Most simply, temporary access can be provided by the direct percutaneous introduction of a needle through the patient's skin and into a blood vessel. While such a direct approach is relatively simple and suitable for applications, such as intravenous feeding, intravenous drug delivery, and which are limited in time, they are not suitable for hemodialysis and other extracorporeal procedures that must be repeated periodically, often for the lifetime of the patient.
For hemodialysis and other extracorporeal treatment regimens, a variety of implantable ports have been proposed over the years. Typically, the port includes an internal chamber and an access region, such as a septum, while the chamber is attached to an implanted catheter which in turn is secured to a blood vessel. In the case of veins, the catheter is typically indwelling and in the case of arteries, the catheter may be attached by conventional surgical techniques.
Of particular interest to the present invention, implantable ports typically include a needle-penetrable septum which permits the percutaneous penetration of a needle into the internal chamber. The chamber, in turn, is connected to one end of the catheter, and the other end of the catheter is indwelling in the blood vessel. While workable, such designs suffer from a number of problems. Repeated penetration of the septum often leads to degradation over time, presenting a substantial risk of small particulates entering the blood stream and/or need to periodically replace the port. The fragility of the septum has necessitated the use of relatively small bore needles, typically 19 gauge needles (having an outside diameter below 1.08 mm and a bore diameter below 0.94 mm) or smaller. Such small needles significantly limit the flow volume that can be delivered to and from the port. While this may not be problematic in drug delivery, it is of concern in high volume applications, such as dialysis, hemofiltration, and the like.
As an alternative to septum-based implantable ports, the assignee of the present application has developed an implantable port having a mechanical valve which replaces the septum component on the septum ports. The valve is actuated by the percutaneous introduction of the needle through an aperture on the valve housing. Since the septum has been eliminated, the needle used to access and actuate such ports having mechanical valves can be much larger than those used to penetrate septums, typically having a size of at least 16 gauge (having an outside diameter of 1.66 mm and a bore size up to 1.5 mm), preferably higher. The use of a larger access needle will permit a much higher volumetric transfer rate for blood or other liquids to be transferred, such as infusates, perfusates, dialysis fluids, and the like.
Heretofore, the assignee of the present application has generally utilized straight needles for accessing the implantable ports having mechanical valves. By "straight needle," it is meant that the needle is aligned parallel to or coaxial with the distal end of the catheter to which it is attached. Such a straight needle attachment can be problematic, particularly since it results in a "high profile" catheter attachment to the skin. The needle or other access tube inserted into the port will generally be oriented in a direction normal to the patient's skin. Thus, the catheter will generally project straight out from the patient's skin, making immobilization of the catheter during use problematic.
For these reasons, it would be desirable to provide access catheter systems capable of vertically accessing an implantable port and incorporating large bore needles to accommodate high fluid transfer rates. Such catheters should be inexpensive to produce, have highly reliable designs, and be compatible with other aspects of the present invention as described below.
A second problem with access catheters and needles relates to the maintenance of sterility. Generally, the patient's skin will be swabbed with alcohol or other disinfectant prior to percutaneous introduction of a needle or other access tube. While such precautions are generally sufficient to prevent infection, the need to repeatedly access the same percutaneous insertion site presents significant risk of infection to the patient.
It would thus be desirable to provide improved access catheters and methods which enhance sterility and inhibit infection resulting from percutaneous needle access. Such apparatus and methods will preferably be capable of delivering a desired antiseptic, antibiotic, anesthetic, or other active agent to the tissue location through which the needle is inserted. Preferably, the apparatus and methods will provide for a prolonged delivery of the desired agents over time, preferably over the entire time period over which the needle is to be maintained in the access port.
At least certain of these objective will be met by the invention described below.
2. Description of the Background Art
Hypodermic needles having absorbent pads carrying an antiseptic are described in U.S. Pat. Nos. 4,243,035; 3,134,380; and 2,693,186. Needles having compressible sheaths for maintaining sterility are described in U.S. Pat. Nos. 4,775,369 and 2,847,995. Needles and other access tubes for percutaneously accessing implanted ports are described in U.S. Pat. No. 5,562,617, as well as co-pending application Ser. Nos. 08/539,105; 08/724,948; 60/036,124; and 08/856,641 (Attorney Docket No. 17742-001700; filed on May 15, 1997), assigned to the assignee of the present application, the full disclosures of which are incorporated herein by reference. Needles and other structures connected and/or connectable to catheters at generally right angles for accessing implanted ports are described in U.S. Pat. Nos. 5,421,814; 5,041,098; 4,955,861; 4,710,174; 4,645,495; 4,464,178; and 4,569,675.